Mechanical counter for a metering apparatus

ABSTRACT

A metering apparatus for metering for example a medicament requires a device with which the number of metering portions is displayed. The known display devices however are not suitable for a metering apparatus having two housing portions which are rotatable relative to each other. The mechanical counter for a metering apparatus of that kind comprises at least one spindle with rotary locking, whose axis extends in parallel relationship with the axis of the metering apparatus and which is disposed in the region of a peripheral surface of the apparatus. The spindle is automatically driven by way of a transmission assembly when the metering apparatus is actuated. The number of metering portions already discharged and the number of petering portions permitted in total is quasi-continuously displayed by the mechanical counter. The transmission ration of the transmission assembly can be designed to cover a wide range. The cursor serving for display purposes can be reset on the spindle. The permissible period of use of a metering apparatus which can be used for a plurality of supply containers can be reliably viewed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns a mechanical counter for a metering apparatus formetering powder, liquid or gaseous substances, and metering apparatuscomprising such a counter. The apparatus comprises inter alia twocoaxially arranged housing portions which are rotated relative to eachother upon actuation of the apparatus. The number of metering portionsof the substance is counted and displayed by the counter.

An aim of the invention is to provide optimum adaptation of a counter ofthat kind to handling of the metering apparatus in an operationallyreliable manner, and to simplify manufacture of the counter.

2. Related Art

The invention has been particularly, though not exclusively, developedfor application to metered dose inhalers (MDI's) such as are disclosedin U.S. Pat. No. 5,497,944 (derived from WO91/14468), the entirecontents of both of which are incorporated herein by reference. Pressure(generally at least 50 bar) is generated in a metered amount of fluidwhich is discharged through a nozzle assembly having one or more verysmall openings e.g. in the range 25 to 500 square micrometres. Preferrednozzle assemblies are disclosed in U.S. Pat. No. 5,472,143 (and parallelWO94/07607), the entire contents of both of which are incorporatedherein by reference. An energy storage means, such as a spring, ispreferably manually loaded e.g. by a rotary sawtooth wedge arrangementas disclosed in U.S. Pat. No. 4,260,082 and GB Patent Application2291135, the entire contents of both of which are incorporated herein byreference. A latching mechanism is generally provided to hold the springin the loaded position and is manually releasable to pressurise themetered amount of fluid e.g. using a piston and cylinder arrangement. Areservoir and valve arrangement can be provided for recharging thecylinder. Further details are described in PCT/EP96/04351 and parallelU.S. Ser. No. 08/726219, the entire contents of both of which areincorporated herein by reference.

Metering apparatuses are used for example in medical aerosol therapy fordealing with ailments of the respiratory tracts. In that situation aliquid or powder medicament is atomised to form an aerosol by means ofan atomiser or entered into a stream of gas. The medicament is containedin a supply container which is inserted into the metering apparatus. Thesupply in a container may be sufficient for several days up to somemonths. It is therefore necessary to display the consumed amount ofmedicament or the amount of medicament which is still present in thecontainer.

PCT Patent Publication WO-93/24167 provides a display device for amedical metering apparatus. That display device comprises a ring whichis rotatable in coaxial relationship with respect to the apparatus andwhich, for each dose of a medicament under pressure which is taken fromthe metering apparatus, is automatically rotated through a predeterminedangle by a wedge drive, a small portion of the ring being visible. Thedisplay device is pneumatically actuated when the medicament is inhaled.

U.S. Pat. No. 4,817,822 discloses a display device for a meteringapparatus, the display device comprising a linear or a rotatabledisk-like scale which is disposed beside the metering device and whichis moved by means of a locked wheel and a locking pawl. Only a smallportion of the scale is visible through a window.

PCT Patent Publication WO-86/05991 describes a display device for ametering apparatus, which device comprises a disk-like scale with teethon the periphery of the disk, and is rotated by means of a helix member.Only a small portion of the scale is visible through a window.

PCT Patent Publication WO-92/09324 discloses a display device for ametering apparatus in which the axial movement of the supply containerwithin the housing is transmitted by means of a locking pawl and a wormgear to a rotatable scale of which a small portion is visible through awindow.

In accordance with PCT Patent Publication WO-86/02275 a display devicefor a medical spray apparatus comprises a digital mechanical counterwhich is advanced by the movement of the supply container within thehousing as soon as a dose of the substance is taken from the supplycontainer. That apparatus comprises a large number of individual parts.

A display device which is actuated pneumatically or mechanically upondisplacement of the supply container, which is under pressure, in thehousing of the metering apparatus, is unsuitable for a meteringapparatus having two housing portions which are rotatable relative toeach other and a supply container which is fixedly disposed in themetering apparatus.

Ways were therefore sought of providing a suitable mechanical counterfor a metering apparatus having two housing portions which are rotatablerelative to each other.

SUMMARY OF THE INVENTION

The invention provides according to one aspect, a mechanical counter fora metering apparatus having two coaxially arranged housing portionswhich are rotatable relative to each other, which includes at least onespindle, whose axis extends substantially parallel to the axis of themetering apparatus, and which is disposed in the region of theperipheral surface of the metering apparatus and which is mounted to thefirst housing portion in the vicinity of each of the spindle ends bymeans of a respective rotary mounting. The spindle has a tootharrangement at the end which is closest to the second housing portion.Provided at the edge of the second housing portion is at least oneprojection which engages into the tooth arrangement at the spindle endupon rotation of the two housing portions relative to each other. Inorder to provide good running properties for the transmission assembly,the tooth arrangement at the spindle end and the projections arepreferably in the form of an involute tooth configuration. Disposed onthe spindle is a cursor with rotary securing (prevention of rotation), ascale being disposed opposite same.

According to another aspect, the invention provides a metering apparatushaving two coaxially arranged housing portions which are rotatedrelative to each other when the metering apparatus is operated, themetering apparatus having a mechanical counter comprising ascrewthreaded spindle mounted in bearing means on one of the housingportions in a peripheral region thereof so that it is rotated bymovement of the other housing portion, and a cursor movable, by thescrewthread, relative to marker means, the arrangement being such thatmovement of the cursor with respect to the marker means provides ameasure of the number of operations of the apparatus.

Preferred features of the counter and the metering apparatus will now bedescribed.

The two housing portions are rotated relative to each other to actuatethe metering apparatus. The angle of rotary movement may be a preferablyintegral fraction of 360 degrees; it is preferably 30 to 360 degrees.The relative movement of the two housing portions relative to eachother,is taken off and converted into a rotary movement of the spindleand a sliding movement of the cursor by means of the transmissionassembly which comprises the tooth arrangement at the one end of thespindle and the at least one projection at the edge of the secondhousing portion. The rotary mountings for the spindle are preferably inthe form of snap-action mountings. The transmission ratio of theprojection-type transmission assembly is fixed by the number ofprojections and the number of teeth on the pinion; that also fixes thenumber of revolutions of the spindle, which corresponds to an actuationof the metering apparatus. For each actuation of the metering apparatusthe number of revolutions of the spindle can be from 1/30th (onethirtieth) to 10. The pitch of the screwthread on the spindle is adaptedto the number of metering portions which can be taken from the supplycontainer in the metering apparatus, and to the travel of the cursor onthe spindle. When the spindle is rotated the cursor on the spindle isdisplaced relative to the scale which is disposed for example on thefirst housing portion. The scale is preferably linearly divided. Theposition of the cursor indicates what proportion of the substance to bemetered has already been taken from the supply container and whatproportion is still present. The direction of rotation of thescrewthread on the spindle is either in the same direction or in theopposite direction to the direction of rotation of the housing portionsrelative to each other.

The cursor substantially comprises a display ring, at least one limbhaving a screwthread portion and at least one further limb with aresetting projection. There are preferably a plurality of limbs and thelimbs are preferably of a resilient nature. The screwthread portionpositively lockingly engages into the screwthread on the spindle. Thecursor can be displaced on the spindle for resetting thereof, by meansof the resetting projection. When the cursor is displaced thescrewthread portions on the resilient limbs slide resiliently over thespindle screwthread without damage. The contours of the cursor and thehousing are so selected that the cursor is prevented from being rotatedon the spindle, by positively locking engagement. For example at leastone of the resetting projections may project beyond the screwthread tosuch a degree that it does not pass through the gap between the spindleand the peripheral surface of the first housing portion. That projectionserves as a rotary securing means for the cursor.

A recess can be provided at the other end of the spindle which is inopposite relationship to the drive portion of the spindle. As soon asthe screwthread portions on the resilient limbs have reached that recessthe cursor ceases to be displaced. The recess serves as a free-motionmeans for the cursor so that damage to the cursor is avoided if theadmissible travel distance of the cursor on the spindle is exceeded uponfurther actuation of the metering apparatus.

Preferably a cover can be fitted over the first housing portion toprotect the metering apparatus and the counter. The cover is connectedto the first housing portion releasably in an axial direction in apredetermined position. The cover when in the condition of being fittedin position cannot rotate relative to the first housing portion.Accordingly the first housing portion can still be rotated with respectto the second housing portion although the first housing portion iscovered by the cover.

The scale which is disposed opposite the cursor is provided either onthe first housing portion or on the inside or the outside of the cover.The cover is transparent in a region-wise manner or it comprisestransparent material.

At least one rigid entrainment means may be provided on the inside ofthe cover, which entrainment means pushes the cursor back into thestarting position thereof at the one end of the spindle by means of theresetting projections when the cover is fitted into place.

Elastic entrainment means may be provided in place of the rigidentrainment means. In this case the resetting projections of the cursorcan be provided with rigid limbs.

When the cursor is reset the cursor abuts against a step at the one endof the spindle before the cover reaches its end position. The cover isfurther moved to its end position, in which case the elastic portion,that is to say the resilient limb or the elastic entrainment means,springs back and the cursor and the entrainment means are uncoupled.Accordingly the cursor is in its starting position from which it isdisplaced when the spindle is rotated.

In a specific configuration of the counter the pinion at the one end ofthe spindle has four teeth of which two oppositely disposed teeth arewider than the other two teeth. Provided on the edge of the secondhousing portion are two projections, between which there is a recess inwhich the wider teeth of the pinion can roll. That transmission assemblypreferably has a transmission ratio of half a spindle revolution to twoactuations of the metering apparatus, for example half a revolution to arotary movement of 360 degrees of the two housing portions relative toeach other.

If a rotational movement of for example 120 degrees of the two housingportions relative to each other is required for actuation of themetering apparatus there may be three projections on the second housingportion, more specifically being displaced through 120 degrees relativeto each other. Furthermore in this case also the projections on thesecond housing portion may be present only singly. Then the spindle isfurther rotated only in each third actuation of the metering apparatus,although each actuation is counted.

The flanks of the wider teeth lie on the inner or outer peripheralsurface of the second housing portion. The spindle is thereforerotatable only when the wider teeth can engage into the opening betweenthe projections. That rotary locking arrangement always holds thespindle in the starting position which is provided at the beginning ofthe rotary movement.

A plurality of supply containers containing the substance to be meteredcan possibly be successively fitted into the metering apparatus andused. If the substance to be metered is for example a medicament it maybe necessary for reasons of hygiene to limit the permitted number ofmetering portions with the re-usable metering apparatus. Then it isadditionally necessary to count and display the total number of meteringportions which have already been discharged with the metering apparatusor the total number of metering portions which are still available. Theabove-described mechanical counter can be developed in various ways tocover that situation.

In a first embodiment of such a development a gear is provided on theother end of the spindle, which is opposite to the drive side. Providedat the corresponding end of the first housing portion is a coaxial ringgear, preferably with a flange, which is mounted rotatably with respectto the first housing portion and into which the gear engages. The ringgear is also rotated through a given angle for each revolution of thespindle.

Provided on the flange is at least one first mark which, after less thana 360 degree rotation of the ring gear relative to the first housingportion and after consumption of a supply container is disposed oppositea second mark which is in a fixed position relative to the first housingportion. The number of marks on the flange is equal to the number ofsupply containers which are permitted as a maximum for the meteringapparatus (or for the substance to be metered). The second mark can bedisposed on the first housing portion or it can be a window in the coverwhich is fitted onto the first housing portion.

The flange can be provided, instead of the marks, with a scale whichquasi-continuously displays the total number of metering portionsdischarged with the metering apparatus or the total number of meteringportions still available, for example in a window. The ring gear isrotated through at most 360 degrees to display the maximum permissiblemetering portions. For that purpose, a high step-up ratio is possiblyrequired between the rotation of the spindle and the rotation of thering gear, that ratio being structurally fixed by means of a suitableratio between the numbers of teeth involved.

In a second embodiment of the development of the counter the counterincludes a second spindle which may be similar to and arranged parallelto the first spindle and which carries a cursor which is possibly notresettable. Provided at one of the two ends of the first spindle is agear which engages into a gear at the corresponding end of the secondspindle. Disposed opposite the cursor on the spindle is a scale in afixed position with respect to the first housing portion, which scalecan be disposed either on the first housing portion or on the coverfitted thereon. In the case of this counter the total number of meteringportions which have already been discharged or the total number ofmetering portions which are still available is represented on thedisplacement travel of the cursor on the second spindle.

In place of the second spindle with cursor, the arrangement may have arotatably mounted roller, on the periphery of which a helical line isdrawn with an entire revolution over the entire length of the roller.The surfaces on the two sides of the helical line are marked indifferent ways, preferably in two colours, for example red and white orred and green. In this construction the cover has a narrow window whichis as long as the roller and through which a narrow strip of theperipheral surface of the roller is visible. A scale can be disposedbeside the window and extends over the entire length of the roller. Thescale can be divided in accordance with the maximum permitted number ofmetering portions or it can be divided into numbered sections accordingto the maximum permitted number of supply containers.

A third embodiment of the development of the counter has a secondspindle which is of a similar design configuration to the first spindlebut which is disposed at another location in the region of theperipheral surface of the metering apparatus. It is provided with atransmission arrangement, similarly to the first spindle, but thetransmission ratio is matched to the total number of permissiblemetering portions. That spindle is driven by projections at the edge ofthe second housing portion, preferably by the projections which arealready used for driving the first spindle.

In order to provide the high step-up ratio which is possibly requiredbetween the first and second spindles or between the first spindle andthe ring gear, the arrangement may have, instead of the gear on thefirst spindle, a single-tooth transmission arrangement with which thegear on the second spindle or the ring gear is further rotated by onetooth for each revolution of the first spindle. The step-up ratio can befrom 2 to 1 to 10 to 1.

The rotary locking means for the spindle or the ring gear (i.e. themeans for inhibiting unwanted movement) may be a locking pawl or therotary locking means lies in the friction between the spindle and themounting or the ring gear and the mounting or in a specificconfiguration of the parts, for example a positively locking toothconfiguration. The cursor is rotationally secured on the spindle byvirtue of the positively locking contour of the cursor.

The components of the counter may consist of virtually any material.They are preferably made from plastics material, for example by aninjection moulding process. For medical purposes, physiologicallyharmless materials are used such as for examplepolybutyleneterephthalate (PBT) or a compound of PBT and Teflon(polytetrafluoroethylene). The materials are preferably so selected thatdifferent materials run against each other, for example PBT with Teflonagainst PBT or PBT against acrylbutadiene-styrene.

The counter according to the invention can be used for example in ametering apparatus which serves as a high-pressure atomiser for a liquidmedicament. The liquid to be atomised is disposed in a pressure-lesssupply container which communicates with a miniaturised high-pressuregenerating means with which an aerosol is generated; for details in thisrespect see German laid-open application (DE-OS) No. 195 36 902.5 (theentire contents of which are incorporated herein by reference). Thedevice for producing the high pressure is operated by means of aspring-actuated locking stressing mechanism, the spring being stressedby rotation of two housing portions relative to each other; for detailsattention is directed to German laid-open application (DE-OS) No. 195 45226.7 (the entire contents of which are incorporated herein byreference). The counter according to the invention is automaticallyadvanced when the housing portions are rotated relative to each other.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 Perspective view of a part of a metering apparatus having acounter

DETAILED DESCRIPTION OF THE DRAWING

A preferred embodiment of the invention will now be described in greaterdetail with reference to the drawing (FIG. 1) which shows part of ametering apparatus having a counter. In this embodiment the firsthousing portion is rotated through 180 degrees relative to the secondhousing portion for actuation of the metering apparatus.

The first housing portion 1 is mounted coaxially rotatably relative tothe second housing portion 2. The cover 3a which is mounted thereonencloses the first housing portion 1 and the counter. The cover isadditionally shown in broken lines in the withdrawn position 3b. Thenumber of metered portions taken from the supply container which is inuse at the time is counted with the spindle (rotary shaft) 4. Thespindle 4 is rotatably mounted on the first housing portion by the twosnap-action mountings 5 and 6 which act as bearings. The groove 7 whichaccommodates mounting 5 serves for axially fixing the spindle. Thecursor with display ring 9 is provided with two resilient limbs 10 eachhaving a respective screwthread engagement portion 11 and two resettingprojections 12 on two limbs 13. The recess 8 is the free-motion meansfor the portions 11 at the end of their travel. Provided on the insideof the cover are two entrainment means 14 which, when the cover isfitted in position, push the cursor 9 back into the starting position atthe end of the spindle by means of the resetting projections 12. Whenthat happens the cursor ring 9 bears against the abutment 15 and thecursor is released as described above.

Disposed at the one end of the spindle is a four-tooth pinion 16 havingtwo (axially) narrow teeth 17 and two (axially) wide teeth 18. The edgeof the second housing portion carries the two projections 19 and 20between which there is the opening 21. As described aboave, the teethand projections are preferably of involute shape. Disposed at the otherend of the spindle is the gear 22 which engages into the ring gear 23.Provided on the flange 24 of the ring gear are a plurality of numberedmarks 25, of which a respective mark appears in the window 26 in thecover 3a after a given rotary movement of the ring gear.

The position of the cursor 9 against marker means in the form of thelabelled scale 27 shows the number of metering portions taken from thesupply container or the number of metering portions which can still betaken therefrom. When the supply container is empty a respective one ofthe numbered marks 25 appears in the window 26.

The illustrated counter incorporates the preferred features of theinvention discussed above (but not the second and third "developments"discussed above) and the description just given should be read inconjunction with earlier discussion of these preferred features.

The preferred counter according to the invention has the followingadvantages:

it is automatically advanced when the metering apparatus is actuated;

it is non-critical in terms of tolerances and is therefore reliable andsure in operation;

the transmission can be designed to cover a wide range;

it displays the number of discharged metering portions and/or the numberof metering portions still available, quasi-continuously and with anadequate degree of accuracy;

it is inaccessible and cannot be displaced by mistake when using themetering apparatus;

it can be used for a plurality of supply containers in succession;

it can be produced for a different number of metering portions from eachsupply container and for a different maximum number of supply containerswhich may be used with a metering apparatus;

it is integrated into the metering apparatus and does not require anysubstantial modification thereof;

it can be produced in miniaturised form and therefore takes up only asmall amount of space;

the individual parts of the counter,are preferably made from plasticsmaterial which operate without lubricant at a low level of friction;

no substances can get into the substance to be metered, from thecounter;

it comprises a small number of individual parts which can beinexpensively produced by injection moulding;

it is easy to assemble;

the counter can be reset each time a supply container is emptied; as aresult the starting position of the cursor on the spindle is clearlyestablished whenever a fresh supply container is introduced;

the combination of a spindle which counts the actuations of the meteringapparatus during use of a supply container with a second spindle or witha ring gear means that the metering apparatus can be reliably used for apredetermined total number of metering portions or for a predeterminedtotal number of supply containers in succession. The period of use ofthe metering apparatus can be reliably reviewed.

What is claimed is:
 1. A mechanical counter for a metering apparatushaving a first housing portion and a second housing portion coaxiallyarranged which are rotated relative to each other when the meteringapparatus is operated, the mechanical counter comprising:a spindle witha screwthread thereon, an axis of which extends substantially parallelto an axis of the metering apparatus and which is disposed in the regionof a peripheral surface of the metering apparatus and which is mountedin the vicinity of ends of the spindle with respective rotary mountingson the first housing portion; at least one projection at an edge of thesecond housing portion, for engaging a tooth arrangement and rotatingthe spindle; a cursor movable along the spindle by the screwthread whenthe spindle rotates; and a scale disposed adjacent to the cursor.
 2. Amechanical counter according to claim 1 wherein said rotary mountingsare snap-action mountings.
 3. A mechanical counter according to claim1,wherein one end of the spindle in the vicinity of the second housingportion is provided with a pinion, said pinion being provided with saidtooth arrangement; and wherein said at least one projection engages withsaid tooth arrangement as the two portions are rotated relative to eachother.
 4. A mechanical counter according to claim 3, wherein said tootharrangement on said pinion includes four teeth, and said at least oneprojection on the second housing portion comprises two projections.
 5. Amechanical counter according to claim 3, whereinsaid pinion includesfour teeth of which two oppositely disposed teeth are wider than theother two teeth, and wherein a flank of the wider teeth bears against aninner peripheral surface of the second housing portion, said at leastone projection comprises two projections on the edge of the secondhousing portion, and wherein an opening between the two projections islarger than the width of the wider teeth of the pinion.
 6. A mechanicalcounter according to claim 1, further comprisinga transmission ratio ofhalf a spindle revolution to two actuations of the metering apparatus.7. A mechanical counter according to claim 1 whereina pitch on thespindle screwthread is matched to the number of the metering portionsand a displacement travel of the cursor.
 8. A mechanical counteraccording to claim 1 whereinthe spindle includes means for inhibitingunwanted movement.
 9. A mechanical counter according to claim 1whereinthe cursor comprises a screwthread engagement portion engageablewith the screwthread on the spindle, and a resilient limb.
 10. Amechanical counter according to claim 9 whereinthe end of the spindlefurthest from said second housing portion comprises a recess forreceiving the screwthread engagement portion of the cursor.
 11. Amechanical counter according to claim 9 comprising a resettingprojection on the the resilient limb.
 12. A mechanical counter accordingto claim 1 further comprisinga cover for the first housing portion,wherein said cover is receivable over the first housing portion in theaxial direction to cover over the spindle, and wherein said cover istransparent in a region-wise manner or comprises transparent material.13. A mechanical counter according to claim 12 furthercomprisingentrainment means on the inside of the cover.
 14. A mechanicalcounter according to claim 1 further comprisinga second spindle withmeans for inhibiting unwanted movement, said second spindle beingarranged in substantially parallel relationship with the first spindle,a cursor secured against rotation on the second spindle, a one-toothtransmission assembly including a projection wheel at one end of thefirst spindle, and a gear at the corresponding end of the second spindlewith which the projection wheel at the end of the first spindle engages,and a scale which is disposed adjacent the cursor on the second spindle.15. A mechanical counter according to claim 14 wherein the secondspindle comprises a roller on which a helical line is drawn with onerevolution over the entire length of the roller and the surfaces on thetwo sides of the helical line are marked in different ways, and thecounter comprises a narrow transparent strip in a cover axiallyreceivable over the first housing portion through which a strip on theperipheral surface of the roller is visible.
 16. A mechanical counteraccording to claim 1 further comprisinga gear on the end of the spindlefurthest from the second housing portion, and a ring gear with which thegear engages, said ring gear comprising means for inhibiting unwantedmovement, and preferably a flange; wherein said ring gear is mountedcoaxially with the first housing portion and is rotatable with respectthereto.
 17. A mechanical counter according to claim 16 furthercomprisinga first marking on the flange of the ring gear, which marking,after less than 360 degree rotation of the ring gear relative to thefirst housing portion, is disposed opposite a second marking which is ina fixed position relative to the first housing portion.
 18. A mechanicalcounter according to claim 17 wherein said second marking is on thefirst housing portion.
 19. A mechanical counter according to claim 17wherein said second marking comprises a window in a cover axiallyreceivable over the first housing portion.
 20. A mechanical counteraccording to claim 1 further comprisinga second spindle with means forinhibiting unwanted movement, said second spindle being arranged in asubstantially parallel relationship with the first spindle, a cursorsecured against rotation on the second spindle, and a one-toothtransmission assembly including a tooth arrangement at an end of thesecond spindle which is closest to the second housing portion, andprojections at the edge of the second housing portion which engage withthe tooth arrangement at the end of the second spindle upon rotation ofthe housing portions relative to each other.
 21. A metering apparatushaving two coaxially arranged housing portions which are rotatedrelative to each other when the metering apparatus is operated, themetering apparatus having a mechanical counter comprising:a spindle witha screwthread thereon, an axis of which extends substantially parallelto an axis of the metering apparatus and which is disposed in the regionof a peripheral surface of the metering apparatus and which is mountedin the vicinity of ends of the spindle with respective rotary mountingson a first of said two housing portions; at least one projection at theedge of a second of said two housing portions, for engaging a tootharrangement and rotating the spindle; a cursor movable along the spindleby the screwthread when the spindle rotates; and a scale disposedadjacent to the cursor.
 22. A metering apparatus according to claim 21which is a metered dose inhaler.
 23. A metering apparatus having twocoaxially arranged housing portions which are rotated relative to eachother when the metering apparatus is operated, the metering apparatushaving a mechanical counter comprising a screwthread spindle mounted inbearing means on one of the housing portions in a peripheral regionthereof so that it is rotated by movement of the other housing portion,and a cursor movable, by the screwthread, relative to marker means, thearrangement being such that movement of the cursor with respect to themarker means provides a measure of the number of operations of theapparatus.
 24. A metering apparatus according to claim 23, wherein thecursor can be temporarily released from the screwthread for resetting.25. A metering apparatus according to claim 23, including means forindicating the number of times the cursor has moved through its path oftravel.
 26. A metering apparatus according to claim 23 wherein thespindle axis is substantially parallel to the axis of rotation of thehousing portions and the spindle has a gear thereon which cooperateswith means on said other housing portion to effect rotation of thespindle.
 27. A metering apparatus according to claim 26 wherein thespindle is rotated during only part of the relative rotation of thehousing portions.
 28. A metering apparatus according to claim 23 whichis a metered dose inhaler.
 29. A mechanical counter according to claim1, wherein the cursor is resettable.